In the field of conveyance of containers, such as bottles, the conveyors that are most frequently used for transporting bottles through a bottling unit include pallet chains. These pallet chains describe closed circuits. The bottles will rest upon the upper sides of the pallet chains. These pallet chains can be juxtaposed together so as to define a conveyance plane.
The small width of the pallets that form these conveyors permits them to move along curved trajectories. The conventional pallet chain, which is usually formed of a stainless steel material, is particularly expensive. These pallet chains are often individually driven. Additionally, the speed differential between a chain within the curve and a chain that is located outside of the curve leads to a relative movement of the containers with respect to each other during a transport from a processing unit in one direction or another. This is not always desirable, for example, when less stable containers have to be conveyed.
As a result, there have been prior art conveyor belts that are better able to move, in a horizontal plane, along curved trajectories which include chain links that are hinged to one another extending over the entire width of the conveyor. These prior art chain links include, at the front and the rear, form a central core with a succession of staggered projections crossed by an opening for the passage of a pivot pin so as to assure the connection of two successive chain links. The openings of at least some of the slots at the front or those at the rear are oblong in shape in order to provide these chain-links with longitudinal mobility with respect to the other. This permits these chain-links to be brought closer to each other on the inner side of a bend of the conveyor belt. The traction that is imparted to the conveyor belt by the appropriate driving means is exerted from one chain link on the other along their length. In the curved portions, this traction force can only be reflected from one chain link to the following through the slots located outside of the bend. Since this traction force is concentrated at the outer edge of the conveyor belt in order to be transferred from one chain link to another through a single slot, this makes the belt particularly fragile. The width of the conveyor belt is necessarily limited. Additionally, it cannot have a bend of more than 90°.
In order to improve this situation, several solutions have been contemplated. One solution consists of attaching a reinforced module to the ends of each chain link. Although the chain-links are formed of plastic, the reinforcement modules are actually formed of metal. This solution does not completely solve the problem and the increases weight of the belt through these metal modules. These metal modules are relatively expensive and are generally unsatisfactory in use.
European Patent No. WO-98/06648 describes the use of pivot pin linking two successive chain links so as to form a conical shape at the end portions. The conicality can only fit a well-defined curve radius.
For conveyor belts having a smaller curved radii, the retransmission of the traction force occurs from one chain link onto the next chain link at a precise point on their length transverse to the axis of the belt. This retransmission of the traction force is carried out in a localized way by means of one or two of the slots of these chain links.